Improvement of nutritional components and in vitro antioxidative properties of soy-powder yogurts using Lactobacillus plantarum

Abstract

This research was the first to demonstrate changes in nutritional compositions (isoflavone and CLA) from the 50% methanol extracts of soy-powder milk (SPM) and soy-powder yogurt (SPY) through fermentation using Lactobacillus plantarum S48 and P1201 strains. The radical scavenging activities and protective effects against oxidative stress in LLC-PK1 cells were also investigated. The average physicochemical characteristics including acidity and viable cell number as well as b-glucosidase activity increased with 0.2 -> 0.7%, 7.5 -> 9.8 log cfu/mL, and 0.03 -> 1.75 U/g in SPYs. Total average isoflavones were considerably reduced (3180.3 -> 2018.3 mu g/g) with the increase of aglycone contents (191.8 -> 770.2 mu g/g), especially, daidzein exhibited the most remarkable increase rate (98.6 -> 460.9 mu g/g; > 4.8 times) during fermentation. The CLA and total phenolics also increased with significant differences (ND -> 1.6 mg/g; 2.4 -> 3.6 mg/GAE/g) between SPM and SPY. Interestingly, the cis-9, trans-11 CLA showed approximately 90% in total content. Moreover, the scavenging capacities against three radicals markedly increased with about 30% in SPYs, as the following order: ABTS > hydroxyl > DPPH. The protective effects on oxidative stress (pyrogallol: O-2(-), SNP: NO, and SIN-1: ONOO-) were also observed high cell viabilities (> 10%) under LLC-PK1 cellular system. Our results suggest that SPY may be utilized as a potent source regarding natural antioxidants and beneficial components for health food and medical uses. Copyright (C) 2018, Food and Drug Administration, Taiwan. Published by Elsevier Taiwan LLC.